Polyalkylene glycol based polymers are well known synthetic lubricants because of their natural lubricity, low volatility and water solubility, as well as their noncorrosive nature to metals. Polyalkylene glycol based polymers are used in compressors, heat-transfer systems, refrigeration, and as a bearing and gear lubricants in severe-service applications. They may also find applications in surface treatment as surfactants. Some of them are suitable to be used in food processing. Polyalkylene glycol based polymers have also been used in the food and beverage industry for lubricating containers on conveyors. See U.S. Pat. Nos. 6,302,263, 6,288,012, 6,427,826, 6,214,777, and 6,495,494.
However, some of the polyalkylene glycols have low cloud points in that the solubility of the polymer in water decreases as the temperature increases. The result is that the polymers tend to phase separate as the temperature increases. The temperature that the polymer and water separate from each other is referred to as the “cloud point” because the phase separation forms a cloudy suspension. At temperatures below the cloud point, the polymer is completely water soluble and the polymer in water forms a clear solution. At the cloud point, the polymer phase separates from the water to form a cloudy suspension. At temperatures above the cloud point, the polymer completely phase separates from the water and the two phases are usually clearly visible.
Phase separation at temperatures above the cloud point is undesirable for several reasons. First, if the product is being pumped out of a container and the polymer and water are in separate layers, only one component will be pumped out at a time. This can lead to an ineffective product, for example when the polyalkylene glycol polymer is being used in a conveyor lubricant. Phase separation will also lead to problems with the dispensing of the polyalkylene glycol polymer due to plugging. Another problem caused by phase separation is dilution. Once phase separation occurs, dilution is more difficult because the viscosity is not uniform throughout the composition. Finally, once phase separation occurs, the polymer layer and the water layer do not return to a mixture once the temperature is lowered below the cloud point.
Use of polyalkylene glycol polymers with relatively low cloud points in compositions is usually very limited. Such polyalkylene glycol polymers typically have storage, shipping, and use limitations in that they cannot be incorporated into compositions that normally would be used as temperatures at or above the cloud point. Therefore, a need exists for compositions containing polyalkylene glycol polymers with increased cloud points.